import time
import gradio as gr

MAX_QUEUE_SIZE = 3

def get_sorted_queue(queue_state):
    if queue_state is None:
        return []
    # Sort by age descending; if ages equal, keep original order by queue number
    return sorted(queue_state, key=lambda p: (-p["Age"], p["Queue No."]))

def add_to_queue(name, age, queue_state):
    if queue_state is None:
        queue_state = []

    if not name:
        return (
            "Please enter your name.",
            queue_state,
            get_sorted_queue(queue_state),
            -1,
            "Waiting for people to join the queue."
        )

    try:
        age = int(age)
        if age <= 0:
            raise ValueError
    except Exception:
        return (
            "Please enter a valid positive age.",
            queue_state,
            get_sorted_queue(queue_state),
            -1,
            "Waiting for people to join the queue."
        )

    if len(queue_state) >= MAX_QUEUE_SIZE:
        return (
            "Queue is full. Only 3 people are allowed.",
            queue_state,
            get_sorted_queue(queue_state),
            -1,
            "Queue is full. No more people can join."
        )

    queue_number = len(queue_state) + 1
    person = {
        "Queue No.": queue_number,
        "Name": name,
        "Age": age
    }
    queue_state.append(person)

    message = f"Welcome, {name}! Your queue number is {queue_number}."
    display_queue = get_sorted_queue(queue_state)

    return (
        message,
        queue_state,
        display_queue,
        -1,
        "Queue updated. Press 'Start / Next' to call the next person."
    )

def reset_queue():
    return (
        "Queue has been reset.",
        [],
        [],
        -1,
        "Waiting for people to join the queue."
    )

def serve_next(queue_state, service_index):
    if not queue_state:
        return (
            "No one in the queue yet.",
            -1,
            [],
            "Waiting for people to join the queue."
        )

    display_queue = get_sorted_queue(queue_state)

    if service_index is None or service_index < 0:
        idx = 0
    else:
        idx = service_index + 1

    if idx >= len(display_queue):
        return (
            "All people have been served.",
            service_index,
            display_queue,
            "Queue completed."
        )

    person = display_queue[idx]

    # Simulate a 10-second service time
    time.sleep(10)

    now_serving_msg = (
        f"Now serving: Queue No. {person['Queue No.']} - "
        f"{person['Name']} (Age {person['Age']})"
    )
    status_msg = "Next person has been called."

    return (
        now_serving_msg,
        idx,
        display_queue,
        status_msg
    )

with gr.Blocks() as demo:
    gr.Markdown("# Smart Queue System (Older First)")
    gr.Markdown(
        "Enter your name and age. Up to 3 people can join the queue. "
        "Older people are served first. Each turn takes about 10 seconds."
    )

    queue_state = gr.State([])
    service_index = gr.State(-1)

    with gr.Row():
        name_input = gr.Textbox(label="Name")
        age_input = gr.Number(label="Age", precision=0)

    with gr.Row():
        submit_btn = gr.Button("Join Queue")
        reset_btn = gr.Button("Reset Queue")
        next_btn = gr.Button("Start / Next")

    status_output = gr.Textbox(label="Status", interactive=False)
    now_serving_output = gr.Textbox(label="Now Serving", interactive=False)

    queue_table = gr.Dataframe(
        headers=["Queue No.", "Name", "Age"],
        label="Current Queue (sorted, older first)",
        datatype=["number", "str", "number"],
        wrap=True
    )

    submit_btn.click(
        fn=add_to_queue,
        inputs=[name_input, age_input, queue_state],
        outputs=[
            status_output,
            queue_state,
            queue_table,
            service_index,
            now_serving_output
        ]
    )

    reset_btn.click(
        fn=reset_queue,
        inputs=None,
        outputs=[
            status_output,
            queue_state,
            queue_table,
            service_index,
            now_serving_output
        ]
    )

    next_btn.click(
        fn=serve_next,
        inputs=[queue_state, service_index],
        outputs=[
            now_serving_output,
            service_index,
            queue_table,
            status_output
        ]
    )

if __name__ == "__main__":
    demo.launch()